Significance Statement

With the recent development of NEMs and MEMs technologies, high heat generation has emerged to be a critical issue. Therefore, for further advances in these systems, the development of a thermal interface material with high heat conductivity is imperative. For this reason, fluids dispersing metal nanoparticles, for instance copper and silver, are being identified as potential candidates for application as thermal interface materials with high heat transfer attributes. Their thermal conductivity potential has been investigated theoretically and experimentally.

Dr. Yuhiro Iwamoto and colleagues from Nagoya Institute of Technology in Japan developed a water-based magnetic suspension dispersing silver nanowires and their thermal conductivity measurements and analysis in the absence and presence of an external magnetic field using the hot-wire method. Other researchers contributed to this study were from Doshisha University and The University of Shiga Prefecture. The work is now published in peer-reviewed journal, Experimental Thermal and Fluid Science.

In their work, a mixture of silver nanowires and water-based magnetic suspension were applied as test fluids for thermal conductivity. Silver nanowires with unique dimensional attributes were realized using the polyol approach with suitable modifications. The silver nanowires produced using polyol process was suspended in water-based magnetic suspension. Thermal conductivity improvement under external magnetic fluid may count on the orientation of the silver nanowires in the tests fluid. In this paper, dark field microscopy approach was adopted to visualize the dynamic behavior of silver nanowires in nanowire dispersed magnetic functional fluid.

The authors observed that when an external magnetic field was imposed on the magnetic suspension, the magnetic moments of the magnetic nanoparticles dispersed in the suspension align themselves in the magnetic field. However, the surfaces of non-magnetic particles of bodies dispersed in the magnetic suspension and exposed to an external magnetic field becomes magnetically charged owing to the magnetization of their surroundings and finally become as magnetic materials.

Thermal conductivity analyses using the fluid dispersing silver nanowires suggested that an enhancement of 7% would be realized by dispersing 0.11% of silver nanowires. This behavior was due to the alignment of the long axis of the silver nanowires in the external magnetic field direction by applying the dark field microscopy measurements. A -7% decreased in thermal conductivity under an external magnetic field applied perpendicular to the temperature gradient direction suggested that these fluids could be used in thermal storage application. Enhancement in thermal conductivity is confirmed by using silver nanowires with high aspect ratio and volume concentration.

This study successfully developed a novel silver nanowire dispersed-magnetic functional fluid was developed and demonstrated its capacity as heat transfer material.

About The Author

Yuhiro Iwamoto is currently an Assistant professor of Department of Electrical and Mechanical Engineering, Nagoya Institute of Technology, Japan. He received B.Eng. (2008), M.Sc. (2010) and Ph.D. of Dr. Eng. (2013) in Doshisha University. He has engaged in researches on experimental and computational fluid mechanics and engineering, involving basic study and application for magnetic functional fluids. He is currently interested in and engages in research on effective utilization of the magnetic functional fluids/materials, e.g. energy conversion, heat and mass transfer, damper, isolator, actuator, energy harvesting, electrochemistry, space engineering, etc. He also numerically approaches these topics using Lattice Boltzmann Method as numerical scheme and General-Purpose of Computing on Graphics Processing Units (GPGPU) as a technique for high performance computing. Many reviewed journal papers have been published in these fields.

About The Author

Balachandran Jeyadevan is currently a full Professor at the Department of Materials Science, The Shiga Prefecture University (since 2010), Japan. He graduated from Moratuwa University, Sri Lanka in 1980 (B.Eng.), obtained M.Eng. from Moratuwa University (1987) and Akita University (1991) and Ph.D. (Eng.) (1994) from Tohoku University. Worked as Research Associate in Tohoku University (1994-1996), Lecturer in Akita University (1996-1999), Associate Professor in Tohoku University (1999-2006), Professor in Tohoku University (2006-2010). He has been engaged in researches on developing synthesis technologies for magnetic, conducting, semi-conductor and catalytic nanostructured materials. His entry to nanomaterials is through the synthesis magnetic oxide nanoparticles, preparation of magnetic fluid dispersing these oxides and studying the magnetic behavior of these particulates in magnetic fluid.

He is currently actively involved in synthesizing unique metallic and alloy nanostructures (nanoparticles, rods and wires) by using a non-aqueous process called “polyol process”. Besides working on the elucidation of the redox mechanism in polyol process during the synthesis of metallic nanostructures, he has been highly successful developing techniques to prepare nanostructures using polyol/alcohol reduction processes and has prepared magnetic, conducting, semi-conducting and catalytic nanomaterials for various engineering applications. For more details visit the URL below. http://metal1.mat.usp.ac.jp/~metal-labo/index.html

About The Author

Dr. Yasushi Ido is a professor and a vice president at Nagoya Institute of Technology, Japan. He received Ph.D. in Engineering from Keio University in 1991. He worked for Hokkaido University from 1991 to 1996.

His main research interests are the basic properties and applications of electromagnetic functional materials such as magnetic fluids and magnetic elastomers.

He is presently Editor-in-Chief of the Journal of the Japan Society of Applied Electromagnetics and Mechanics.

About The Author

Dr. Hiroshi Yamaguchi is a professor in Department of Mechanical Engineering, Doshisha University, Japan. He obtained his Ph.D. in Mechanical Engineering from University of Manchester Institute of Science and Technology (UMIST), U.K. in 1982. He is a vice-chairman of International starring committee on Magnetic Fluids.